Method and apparatus for blowing sponge rubber



1937. c. J. RANDALL 2,096,338

METHOD AND APPARATUS FOR BLOWING SPONGE RUBBER Filed Feb. 6, 1955 4 Sheets-Sheet l INVENTOR 7 09mm M mzz .A'ITORNEY 0a. 19, 1937. J, RANDALL 2,096,338

METHOD-AND APPARATUS FOR BLOWING SPONGE RUBBER Filed Fe b. 6,1935 I 4 Sheets-Sheet 2 \Q\ mUi ATTORNEY Oct. 19, 1937. c. J. RANDALL METHOD AND APPARATUS FOR BLOWING SPONGE RUBBER Filed Feb. 6; 1935 4 Sheets-Sheet 5 ATTORNEY C. J. RANDALL Oct. 19, 1937'.

METHOD AND APPARATUS FOR BLOWING SPONGE RUBBER Filed Feb. 6, 1935 4 Sheets-Sheet 4 ATTORNEY Patented Oct. 19, 1937 UNITED STATES PATENT OFFICE METHOD AND APPARATUS FOR BLOWING SPONGE RUBBER Application February 6,1935, Serial No. 5,209

13 Claims.

This invention relates to an improved method and apparatus for making sponge rubber and more particularly for making sponge rubber in continuous sheets.

In the manufacture of sponge rubber a gas forming or blowing agent is mixed with the raw rubber stock and when the stock is heated while it is'being cured, small bubbles of gas are formed therein which expand or blow the stock and make it spongy. .Heretofore in accordance with expands to fill the mold and form the article of the desired shape. Due to the fact that the mold is only partially filled upon the beginning of the expansion of the rubber, no pressure is applied to its top surface and an excess of gas sometimes accumulates near that surface and causes blisters in that portion of rubber.

' A further disadvantage is encountered in blowing rubber in direct contact with the metal of the mold. As themetal is impervious to the blowing gases, it prevents them from escaping from the surfaces. of the rubber in contact therewith, particularly the bottom and sides of the stock, and causes a skin of dense rubber to be formed on such surfaces of the blown rubber.

It has been proposed to blow sponge rubber by placing the raw stock between strips of fabric of a limited lengthand pull the strips containing the stock through a heated zone. In that manner it was possible to eliminate the dense skin on the cured rubber by providing a means for the escape of surface gases through the fabric but as the length of the strips of fabric was limited so were the cured sheets of rubber. Furthermore, as the volume of the heating zone was constant, it was necessary to provide a free space for the stock to expand into upon being .blown. At the beginning of the blow no pressure was applied to the top surface of the stock and'blisters were sometimes formed in the rubber while the stock was expanding to fill the mold. V

In accordance with this invention the above difficulties in blowing sponge rubber are obviated and an improved method and apparatus have been provided for blowing'sponge rubber in continuous sheets in which the raw sponge rubber stock is placed between two endless conveyors of porous material, preferably of fabric, travelling at the same speed between heated platens. The platens are so arranged that they press the conveyors into contact with the sponge stock with regulatable pressure. At least one set of the platens and conveyors is adapted to yield to the expansion of the rubber. In this manner a sheet of rubber of indefinite length may be continuously carried between the platens while the desired pressure is applied to the sur faces of the sponge stock while it is being blown and vulcanized. Since the top and. bottom surfaces of the raw stock is in continuous contact with the heated conveyors and the desired pressure is applied to the top surface of the stock, the rubber is eificiently blown and blisters are prevented. The porosity of the fabric conveyors allows escape of the gas formed during the blowing action and thereby produces sponge rubber of uniform density and eliminates the dense skin of rubber which is formed by the usual practice where the sponge rubber is blown in contact with metal.

The above advantages and important features of this invention will be understood by referring to the following description and the accompanying drawings, in which:

Figure 1 is a plan view of the entire apparatus showing feed rolls from which the supply of raw sponge rubber may be supplied to the machine;

Fig. 2 is a side elevation of the entire apparatus shown in Fig. 1;

Figs. 3 and 4, respectively, are enlarged plan and side elevational views of a portion of the apparatus as shown in Figs. 1 and 2, the supply feed rolls and a portion of the conveyor belts being omitted;

Fig. 5 is a cross section taken on line 5-5 of Fig. 3;

Fig. 6 is a lateral cross section through a portion of the platens;

Fig. 7 is an enlarged view of the portion of the cross section in Fig. 6 showing the sponge stock between the conveyor belts on an enlarged scale; and

Fig. 8 is a cross section of a portion of a sheet of material containing a lamination of sponge stock to be blown in accordance with this invention.

Referring to Figs. 1 and 2 of the drawings, the raw sponge rubber stock is supplied from a pair of stock reels I0 positioned at the head of the apparatus, but it will be understood that the stock .of the expansion of the rubber.

tacky material back to back. The sheets Hare fed in that relationship to abottom. conveyorlz which transports the two superimposed sheets to and underneath a top conveyor I3. The sheets of material II positioned between the conveyors I2, [3 are carried thereby between a top platen I4 and a bottom platen I5. Both of the platens are heated and the top platen I4 is adapted-to yieldably ride upon the top conveyor I3 and hold .it with a regulatable pressure against the sheet material .II. When the machine is operating upon the sponge rubber, the heating chamber containing the rubber between the conveyorsincreases .in cross sectional areain the direction of movement of the conveyors therein to take care The increasein the cross sectional area of the heating chamber 'may be produced by the expansion of the sponge rubber orthe distance between the platens may be initially greater towards the rear to provide for such-increase. V e

The supply rolls II] are rotatably mounted on a frameA having a pair of end posts I5 which supports the front end of the conveyors I2 and. I3.

The platens I4 and I5 are supported on a frame B having a front pair of end posts 22 and a rear pair of end posts 23 on which are journalled driving rolls I1 I8, I8 and20 from which the conveyors .I2 and I3 are driven. The pairs of end posts 22 and23 are braced cross-wise at the topfand bottom by braces 24 and lengthwise by topand bottom sidesills '25 and .26. The top side sills 25 include a long member..25a secured 'to the end posts 22 and 23 and ashort mem'ber25b One of the. side sills 25 is supported intermediate its" ends by .shortstakes 21and the other side sill 25 is supported [by dividedltall side stakes 28 upon which the top platen I4 is yieldably carried as will be hereinafter explained;

The bottom platen I5 is carried by a subframe comprising cross supports. 29 resting upon the side-sills 25. A pair of longitudinal interiorly 'disposed' beams 30 rest upon thecross supports 29 and support the platen I5, which is secured thereto by clamps 3| andscrews32 (Fig. 6).

.Preferably the top platen I4 is made in a'pluralityof sections Ma, I41), I40 and Md so that a different pressure may be applied to conveyor lit at different points. As shown in Fig.5, each section is independently mounted on the tall side stakes 28 and the pressure exerted by each' on theconveyor I3 is controlled by balancing devices each comprising a bell crank lever 33 pivoted ona pin at its elbow withinthespace at the top'of the tall side stakes 28. One arm 35 of the bell lcrank lever 33 overhangsthe sections 50f thetop platen I4 and'is pivoted thereto ona stub shaftl35 journaled in a bracket 37 secured to the platen. The other arm 38 of the bell cranklever 33 extends downwardly within the space in thedivided tall side stake 28 to the bottom of the machine and is resilientlypressed inwardly by. a coiled spring 39 which isheld .under compression between a shoulder 40 on the frame of .themachineand a head M on a rod 42 which extends through the spring and the shoulder on the frame and a bore 7 t in the lower end of the bell crank arm 38. The end of the rod 42 extending through the arm 38 is provided with a nut 43 threaded thereon which holds the rod 42 in cooperative relation with the end of the bell crank arm 38.

There are times when it is necessary to lift the 7 top platen I4 to permit the conveyors I2 and I3 to be changedor to be lifted for other reasons and for this purpose a lifting device is provided for each section of the platen. The lifting device comprises aplurality of air cylinders 44 which are pivoted at one end on a pin 45 to a bracket 46 secured to the frame of the machine (Fig.5). A

piston rod 41 secured'to a piston in each cylinder 44 is attached to the lower end of the downwardly extending arm 38 of each bell crank lever 33.

Each of the cylinders 4- 3 is connected to an air line 48 which may besuitably controlled by a com mon valve (not shown) for simultaneously admitting and discharging air to and from each of the cylinders and thereby cause the piston rods 41 to pull the-arm 38 of the bell crank levers 33 inwardly, as viewed in Fig. 5, and move each section of the top platen and the bell crank levers to the position indicated by the dot and dash lines.

In order to maintain a predetermined minimum space between'the adjacentsurfaces of the platens Hand I5, a stop in the fo-rm of a set screw 49 is provided for each section (Fig. 6). The set screws 49 are threaded through an extension on the top platen I4 and are provided with areduced portion 50 which extends into a slot 5| in a corresponding extension 52 on the bottom platen l5. A shoulder 53 is provided on the screws 49 at the junction between the re-.

duced portion of the set screws and threads. The shoulder 53 rests upon the-top surface of the extension 52 on the bottom platen and maintains the adjacent surfaces of the platens at a prede-. termined distance from-one another inorder to assist in'controlling a minimum thickness of the spongerubber held between the conveyors i2 and I3. The reduced portion 50 of the set screw cooperating with the sides of the slot 5 I- in the ex tension 52 on the bottom platen I5 maintains the .sections'of the top platen in longitudinal align ment with the bottom platen and at the same time permits the top platen to move up and down 'with'respect to the bottom platen.

Theplatens'l l and I5 are heated'by any .vided in each of the platens for the circulation of steam therethrough. Referring to Figs. 3 and suitable medium. Preferably they are'heated byj i steam. As shown in Fig. 6, passages 54are pro-' .5, th'esteam is admitted to the top and bottom' 7 55 co'n nected to the first section of each platen. The sections of the top platen I4 are each connect'ed by a hose connection 56 extending from oneto the other and the sections of the bottom platen I5 are similarly connected, In this manner the steam is circulated through each section Loflthe. platens. I4 and I5 and is exhausted from the respective top and bottom rear platens through steam outlets 51. The supply of steam to .the inlet hoses 55 maybe suitably controlled .by"va1ves, not shown. ,H'eat insulating mate rial 58 (Fig. 6 such as asbestos, is applied to the outsidesurfaces of the platens to prevent heat losses.

Theconveyors I2and I3 are made of pervious material Lin-'gorder tovp'e'rmit the escape of the blowinggase's from the sponge rubber sheet II. Preferably the conveyors I2 and I3v are made platens I4 and I5 respectively through inlet hoses of cotton fabric. :The top conveyor I3 upon emerging from between the upper and lower platens I4 and I5 passes around the driving roll I8 keyed. to a shaft 59 journaled on posts 23. The conveyor I3'passes around the roll I8 and over an idler roll 60. From the idler roll 69 the conveyor I3 passes upwardly over the driving roll I! affixed to ashaft GI journalled to the tops of the end posts 23. The top of the conveyor I3 extends to the head section A of the machine and around roll 62 journalled in the brackets 63'on posts I6. The conveyor I3 then passes backward over a roll 64 journaled in brackets 65 on the posts 22, and'from this roll the conveyor I3 extends downwardly around a roll 66 adapted totake up slack in the conveyor I3 and upwardly over a roll 61 journalled in the brackets 65.

From the latter roll 6! the conveyor I3 extends downwardly and underneath a roll 68 journalled between the forward posts 22 of the section B of th e machine. This roll 68 has its lower circumference positioned substantially opposite the heating chamber between the platens in order to guide the conveyor I3 into the chamber.

The bottom conveyor I2 upon emerging from the space between the platens I4 and I5 passes overthe driving roll I9 which is secured to a shaft 69 journalled on the posts 23 of the machine. The conveyor I2 then passes around the driving roll I9 and over an idler roll I9, then downwardly around the driving roll 29 which is fixed to a shaft II. The bottom side of the bottom conveyor I2 then passes to the head of the machine and over a roll I2 journalled in brackets I3 affixed tothe forward pair of posts 22 and then passes downwardly and underneath a floating take-up roll I4 and upwardly over a .roll Ii-journalled in the same brackets 13. From this position the conveyor I2 extends around a roll I6 journalled in brackets TI on posts I 6 of front section A of the machine which carries the V supply rolls ID of rubber and from the latter roll E6 the conveyor. I2 passes backward over a table I8 to the space between the platens I4 and I5. When it is desired to remove the conveyors I2 and I3 or to release tension therein, the slack take-up rolls 66 and I4 for both the bottom and top conveyors I2 and I3 may be raised and held sprocket 95 fixed to a sleeve 86 journalled on the shaft II to which the lower driving roll 20 of the bottom conveyor I2 is fixed. A smaller sprocket 97 is fixed to the sleeve 85 and drives a chain 88- which meshes with an idler sprocket 89, and

' sprockets 9!], 9i fixed, respectively, to the shafts 59, 69 of the adjacent driving rolls I 8, I9. The upper driving roll II of the upper conveyor I3 and the lower driving roll 20 of the lower conveyor I2 are respectively driven by sprockets 92, 92' fixed respectively to the shafts 59 and 69 which drive chains 93, 94 meshing respectively with sprockets 95, 96 fixed to the shaft 6| and II respectively.

A cross section of a sheet of laminated material particularly suitable for making inner soles for shoes is shown in Fig. 8, which has been prepared for treatment in accordance with this invention.

.The sheet comprises a bottom layer of semi-cured impervious gum rubber stock 91 cemented to an intermediate layer of rag stock 98 which in turn is cemented to a top layer of raw sponge rubber stock 99.

In the operation of this apparatus for the treatment of the above material, the laminated sheets I I I of such material are wound upon reels I9 with the layer of impervious gum stock 9! forming the outer convolutions of the material on the reel. Since the impervious gum stock is semi-cured, it does not adhere to the tacky raw sponge stock material in contact therewith. But it will be obvious that other methods may be used for preventing the convolutions of the sheet material from adhering to one another. The sheet material II is unwound from the reels I9 simultaneously so that the non-tacky gum stock 9'! on the respective sheets is positioned in a back to back relation to each other as shown in Fig. 7. The conveyors I2 and I 3 having been set in motion by the driving motor 89, each of the sheets II is fed in the above relationship on to the bottom conveyor I2 and is conveyed thereby between it and the top conveyor I3 through the heating chamber formed between the top and bottom platens I4 and I5. The sections Ma, Mb, I40 and Md ride upon the top conveyor I3 and force it with a regulatable pressure in contact with the raw sponge stock 99. The pressure exerted by each of these sections upon the conveyor I3 increases progressively in the direction of travel of the sponge stock material that is being blown by the heat transmitted through the conveyors from the heating platens I4 and i5. As the sponge stock is soft and may be easily deformed, the forward section Ma rides comparatively light upon the conveyor I3 so that the material will not be deformed but with enough pressure on the sponge stock to efii-ciently transmit the heat to the stock and also prevent blisters from being formed on the top surface which may result as a lack of pressure. The last section Md is caused to ride upon the conveyor I3 with sufficient pressure to hold the sponge stock that is being blown to the proper gauge but the pressure exerted by any one section is insufficient to cause the rubber to impregnate the conveyors. As the sponge stock travels between the conveyors, the pressure exerted by the sections of the platens on the stock ing chamber having a cross sectional area which increases in the direction of travel of the stock. The conveyors being made of the porous fabric material, they'permit the blowing gases to escape .and prevent the formation of a dense skin on the surface of the blown stock. As the blown and cured sheet material I I passes from the conveyors I2 and I3 at the rear driving rolls I9 and I9, it may be wound upon reels (not shown) and stored for use.

While this invention has been described particularly with reference to blowing and curing sponge stock in a laminated sheet, it will be understood that sheets of raw sponge stock may be fed to the conveyor belts I2 and I3 and blown and cured in a continuous homogeneous sheet in the same manner as the laminated sheets II. It will also be understood that other modifications and details of this invention may be made without departing from the scope of the appended claims.

ing pressure on the sponge stock by the opposed surfaces, heating the stock, and expanding the volume of the stock in the direction of lines normal to the surfaces while in contact therewith.

D 2. The method of blowing sponge rubber comprising the steps of inserting sponge stock between opposed surfaces, one of which is yieldable, transmitting pressure from the yieldable surface to the stock, heating the stock, and expanding it in the direction of the yieldable surface while progressively increasing the pressure on the stock.

3. The method of blowing sponge rubber comprising the steps of continuously passingsponge rubber stock between heated surfaces movable away from one another; heating the stookduring its travel for a sufiicient period to blow the rubber, and thereby move one of the surfaces away from the other.

4. The method of blowing sponge rubber comprising inserting unblown sponge rubber stock between strips of fabric, drawing said strips between heated surfaces, and blowing said stock while substantially the entire area of the opposite surfaces of said strips between said heated surfaces are respectively maintained in contact with the stock and the heated surfaces during the travel of the strips between the surfaces.

5. The method of blowing sponge rubber comprising the steps of inserting sponge stock between strips of fabric, drawing the strips between heated surfaces, transmitting pressure from the heated surfaces to the stock and continuously expanding the stock under the pressure of the heated surfaces in the direction of the distance between the heated surfaces while the strips remain substantially continuously in contact with the heated surfaces.

"6. The method'of blowing sponge rubber comprising the steps of inserting sponge stock be-' tween strips of fabric, drawing the strips between heated surfaces, transmitting a progressively increasing pressure from the heated surfaces to the stock, and continuously expanding the stock under the pressure of the heated surfaces in. the direction of the distance between the heated surfaces while the strips remain substantially continuously in contact with the heated surfaces.

7. The method of making continuous composite sheets having a lamination of spongerrubber, comprising the steps of forming acomposite sheet containing a lamination of raw sponge rubber stock and a layer of uncured dense rubber stock; inserting the composite laminated sheet between two conveyors, one of the conveyors being adjacent to the sponge stock and being adapted to permit the escape of the blowing gases from the surface of the sponge stock, drawing the conveyors and the stock therebetween through a heated zone, and applying alight pressure by the conveyors to the stock during the entire passage through the heated Zone.

8. The method of making continuous composite sheets having a lamination of sponge rubber comprising the steps of forming composite sheets containing a lamination of raw sponge rubber stock and a layer of partially cured dense rubberstock, inserting two of' the composite sheets between two conveyors with the laminations of dense stock back to back, drawing the conveyors and the stock therebetween through a heated zone, and applying'a light pressure to the stock while passing through the heated zone.

9. A sponge rubber blowing machinecomprising'a heating chamber having a movable heating surface, means for yieldably supporting said sur faceso that it is movable in response to the blowing pressure of the sponge rubber during the 7 operation or the machine. 7

10. A sponge rubber blowing machine comprising a heatingchamber, means for drawing sponge rubber stock through said chamber, and said chamber having a cross-sectional area which 7 increases in the direction of the movement of said drawing means.

11. A sponge rubber blowing machine comprising a heating chamber, means for drawing sponge stock through said chamber, said chamher having a movable wall floating upon said porting oneof said platens in respect to the other so that said yieldably supported platen of the machine, a pair: of fabric conveyors extending between and in substantially continuous contact with the opposed surfaces of said platens for conveying sponge rubber stock therebetween and through the heating chamber.

13 A sponge rubber blowing machine comprising a pair of heating platens, one of said platens being made in sections and forming with the other platen a heating chamber therebetween,

means for yieldably supporting said sectional platen, a pair of endless fabric conveyors extending between said platens for; conveying sponge rubber stock therebetween and through V the heating chamber, said platens being adapted will yield in response to the blowingrpressure of the sponge rubber during the normal operation to exert pressure on said conveyors, and meansfor varying the pressure exerted by each section of thesectional platen. 1

: r CHESTER JQRANDALL. 

